An integrally extrusion-molded product in which an outer surface of a metal core material is pressed and coated with a thermoplastic resin is used as a construction member and the like. Patent Document 1 describes an integrally extrusion-molded body having a coating layer containing a polyolefin resin and wood flour on the outer surface of a core material made of metal such as aluminum and having a high-quality wooden texture.
In such an integrally extrusion-molded body, a hollow core material is used in many cases for weight reduction and the like. In that case, the core material can be deformed by a resin pressure during integral extrusion molding for providing the coating layer. In order to cope with this problem, Patent Document 2 describes an integrally extrusion-molded body in which a reinforcing partition member is provided inside the aluminum core material, and a relationship between a thickness of the core material and a span of the reinforcing partition member is regulated.